Electroless plating requires stringent control of the reaction chamber environment and the plating solution. Current electroless plating systems either dispense electrolyte on a spinning wafer or immerse the wafer in a bath of the electrolyte fluid. With these systems, control of the electrolyte over time is difficult. With a spinning wafer, a fair amount of fluid is lost as the wafer spins. With the bath system, the entire bath must be dumped and replaced periodically. Thus, in either of these cases relatively large volumes of the electrolyte solution are consumed for the processing as compared to the amount actually used for the electroless plating. This results in significant waste, not to mention the control issues centered around the chemical bath system. In addition, the attention required for the control of the plating solution and the need to dump and replace the chemical bath cuts into the throughput.
Another drawback with the current systems is that the plating bath must be maintained at an elevated plating temperature. This elevated temperature leads to the degradation of certain additives, e.g., reducing agents, especially with respect to electroless plating techniques that deposit cobalt layers.
In view of the forgoing, there is a need for an electroless plating method and system that can achieve a high throughput with minimal waste.